Do what you feel most comfortable doing. It won't hurt to have a couple of days of the lower dose. Worrying about taking the full dose will only add to your anxiety.
If you have low morning cortisol, you could look into the circadian T3 method. It involves taking the first dose 1.5 hours before you would normally get up. This has been shown, in many people, to increase morning cortisol and aid adrenal recovery. It would be best to read about it properly first to make sure you are doing things right if you decide to follow this route. However, you may find your cortisol sorts itself out just from having some T3.
You could take your first dose of T3 first thing and then, if you feel ok in the afternoon, you could take the second dose. It has a fairly short half-life so is out of your system quite quickly so you may find you get tired in the afternoon while you are just taking the one dose.
I hope it works for you. Hopefully you will find your anxiety lessens after you have been on T3 for a while